mcs/mcs/iterators.cs

   1 //
   2 // iterators.cs: Support for implementing iterators
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Dual licensed under the terms of the MIT X11 or GNU GPL
   9 // Copyright 2003 Ximian, Inc.
  10 // Copyright 2003-2008 Novell, Inc.
  11 // Copyright 2011 Xamarin Inc.
  12 //
  13
  14 using System;
  15 using System.Collections.Generic;
  16 using Mono.CompilerServices.SymbolWriter;
  17
  18 #if STATIC
  19 using IKVM.Reflection.Emit;
  20 #else
  21 using System.Reflection.Emit;
  22 #endif
  23
  24 namespace Mono.CSharp
  25 {
  26         public abstract class YieldStatement<T> : ResumableStatement where T : StateMachineInitializer
  27         {
  28                 protected Expression expr;
  29                 protected bool unwind_protect;
  30                 protected T machine_initializer;
  31                 int resume_pc;
  32                 ExceptionStatement inside_try_block;
  33
  34                 protected YieldStatement (Expression expr, Location l)
  35                 {
  36                         this.expr = expr;
  37                         loc = l;
  38                 }
  39
  40                 public Expression Expr {
  41                         get { return this.expr; }
  42                 }
  43
  44                 protected override void CloneTo (CloneContext clonectx, Statement t)
  45                 {
  46                         var target = (YieldStatement<T>) t;
  47                         target.expr = expr.Clone (clonectx);
  48                 }
  49
  50                 protected override void DoEmit (EmitContext ec)
  51                 {
  52                         machine_initializer.InjectYield (ec, expr, resume_pc, unwind_protect, resume_point);
  53                 }
  54
  55                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
  56                 {
  57                         expr.FlowAnalysis (fc);
  58
  59                         RegisterResumePoint ();
  60
  61                         return false;
  62                 }
  63
  64                 public override bool Resolve (BlockContext bc)
  65                 {
  66                         expr = expr.Resolve (bc);
  67                         if (expr == null)
  68                                 return false;
  69
  70                         machine_initializer = bc.CurrentAnonymousMethod as T;
  71                         inside_try_block = bc.CurrentTryBlock;
  72                         return true;
  73                 }
  74
  75                 public void RegisterResumePoint ()
  76                 {
  77                         if (resume_pc != 0)
  78                                 return;
  79
  80                         if (inside_try_block == null) {
  81                                 resume_pc = machine_initializer.AddResumePoint (this);
  82                         } else {
  83                                 resume_pc = inside_try_block.AddResumePoint (this, resume_pc, machine_initializer);
  84                                 unwind_protect = true;
  85                                 inside_try_block = null;
  86                         }
  87                 }
  88         }
  89
  90         public class Yield : YieldStatement<Iterator>
  91         {
  92                 public Yield (Expression expr, Location loc)
  93                         : base (expr, loc)
  94                 {
  95                 }
  96
  97                 public static bool CheckContext (BlockContext bc, Location loc)
  98                 {
  99                         if (!bc.CurrentAnonymousMethod.IsIterator) {
 100                                 bc.Report.Error (1621, loc,
 101                                         "The yield statement cannot be used inside anonymous method blocks");
 102                                 return false;
 103                         }
 104
 105                         if (bc.HasSet (ResolveContext.Options.FinallyScope)) {
 106                                 bc.Report.Error (1625, loc, "Cannot yield in the body of a finally clause");
 107                                 return false;
 108                         }
 109
 110                         return true;
 111                 }
 112
 113                 public override bool Resolve (BlockContext bc)
 114                 {
 115                         if (!CheckContext (bc, loc))
 116                                 return false;
 117
 118                         if (bc.HasAny (ResolveContext.Options.TryWithCatchScope)) {
 119                                 bc.Report.Error (1626, loc, "Cannot yield a value in the body of a try block with a catch clause");
 120                         }
 121
 122                         if (bc.HasSet (ResolveContext.Options.CatchScope)) {
 123                                 bc.Report.Error (1631, loc, "Cannot yield a value in the body of a catch clause");
 124                         }
 125
 126                         if (!base.Resolve (bc))
 127                                 return false;
 128
 129                         var otype = bc.CurrentIterator.OriginalIteratorType;
 130                         if (expr.Type != otype) {
 131                                 expr = Convert.ImplicitConversionRequired (bc, expr, otype, loc);
 132                                 if (expr == null)
 133                                         return false;
 134                         }
 135
 136                         return true;
 137                 }
 138
 139                 public override object Accept (StructuralVisitor visitor)
 140                 {
 141                         return visitor.Visit (this);
 142                 }
 143         }
 144
 145         public class YieldBreak : ExitStatement
 146         {
 147                 Iterator iterator;
 148
 149                 public YieldBreak (Location l)
 150                 {
 151                         loc = l;
 152                 }
 153
 154                 protected override bool IsLocalExit {
 155                         get {
 156                                 return false;
 157                         }
 158                 }
 159
 160                 protected override void CloneTo (CloneContext clonectx, Statement target)
 161                 {
 162                         throw new NotSupportedException ();
 163                 }
 164
 165                 protected override bool DoResolve (BlockContext bc)
 166                 {
 167                         iterator = bc.CurrentIterator;
 168                         return Yield.CheckContext (bc, loc);
 169                 }
 170
 171                 protected override void DoEmit (EmitContext ec)
 172                 {
 173                         iterator.EmitYieldBreak (ec, unwind_protect);
 174                 }
 175
 176                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 177                 {
 178                         return true;
 179                 }
 180
 181                 public override Reachability MarkReachable (Reachability rc)
 182                 {
 183                         base.MarkReachable (rc);
 184                         return Reachability.CreateUnreachable ();
 185                 }
 186
 187                 public override object Accept (StructuralVisitor visitor)
 188                 {
 189                         return visitor.Visit (this);
 190                 }
 191         }
 192
 193         public abstract class StateMachine : AnonymousMethodStorey
 194         {
 195                 public enum State
 196                 {
 197                         Running = -3, // Used only in CurrentPC, never stored into $PC
 198                         Uninitialized = -2,
 199                         After = -1,
 200                         Start = 0
 201                 }
 202
 203                 Field pc_field;
 204                 StateMachineMethod method;
 205                 int local_name_idx;
 206
 207                 protected StateMachine (ParametersBlock block, TypeDefinition parent, MemberBase host, TypeParameters tparams, string name, MemberKind kind)
 208                         : base (block, parent, host, tparams, name, kind)
 209                 {
 210                         OriginalTypeParameters = tparams;
 211                 }
 212
 213                 #region Properties
 214
 215                 public TypeParameters OriginalTypeParameters { get; private set; }
 216
 217                 public StateMachineMethod StateMachineMethod {
 218                         get {
 219                                 return method;
 220                         }
 221                 }
 222
 223                 public Field PC {
 224                         get {
 225                                 return pc_field;
 226                         }
 227                 }
 228
 229                 #endregion
 230
 231                 public void AddEntryMethod (StateMachineMethod method)
 232                 {
 233                         if (this.method != null)
 234                                 throw new InternalErrorException ();
 235
 236                         this.method = method;
 237                         Members.Add (method);
 238                 }
 239
 240                 protected override bool DoDefineMembers ()
 241                 {
 242                         pc_field = AddCompilerGeneratedField ("$PC", new TypeExpression (Compiler.BuiltinTypes.Int, Location));
 243
 244                         return base.DoDefineMembers ();
 245                 }
 246
 247                 protected override string GetVariableMangledName (LocalVariable local_info)
 248                 {
 249                         if (local_info.IsCompilerGenerated)
 250                                 return base.GetVariableMangledName (local_info);
 251
 252                         return "<" + local_info.Name + ">__" + local_name_idx++.ToString ("X");
 253                 }
 254         }
 255
 256         class IteratorStorey : StateMachine
 257         {
 258                 class GetEnumeratorMethod : StateMachineMethod
 259                 {
 260                         sealed class GetEnumeratorStatement : Statement
 261                         {
 262                                 readonly IteratorStorey host;
 263                                 readonly StateMachineMethod host_method;
 264
 265                                 Expression new_storey;
 266
 267                                 public GetEnumeratorStatement (IteratorStorey host, StateMachineMethod host_method)
 268                                 {
 269                                         this.host = host;
 270                                         this.host_method = host_method;
 271                                         loc = host_method.Location;
 272                                 }
 273
 274                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 275                                 {
 276                                         throw new NotSupportedException ();
 277                                 }
 278
 279                                 public override bool Resolve (BlockContext ec)
 280                                 {
 281                                         TypeExpression storey_type_expr = new TypeExpression (host.Definition, loc);
 282                                         List<Expression> init = null;
 283                                         if (host.hoisted_this != null) {
 284                                                 init = new List<Expression> (host.hoisted_params == null ? 1 : host.HoistedParameters.Count + 1);
 285                                                 HoistedThis ht = host.hoisted_this;
 286                                                 FieldExpr from = new FieldExpr (ht.Field, loc);
 287                                                 from.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
 288                                                 init.Add (new ElementInitializer (ht.Field.Name, from, loc));
 289                                         }
 290
 291                                         if (host.hoisted_params != null) {
 292                                                 if (init == null)
 293                                                         init = new List<Expression> (host.HoistedParameters.Count);
 294
 295                                                 for (int i = 0; i < host.hoisted_params.Count; ++i) {
 296                                                         HoistedParameter hp = host.hoisted_params [i];
 297                                                         HoistedParameter hp_cp = host.hoisted_params_copy [i] ?? hp;
 298
 299                                                         FieldExpr from = new FieldExpr (hp_cp.Field, loc);
 300                                                         from.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
 301
 302                                                         init.Add (new ElementInitializer (hp.Field.Name, from, loc));
 303                                                 }
 304                                         }
 305
 306                                         if (init != null) {
 307                                                 new_storey = new NewInitialize (storey_type_expr, null,
 308                                                         new CollectionOrObjectInitializers (init, loc), loc);
 309                                         } else {
 310                                                 new_storey = new New (storey_type_expr, null, loc);
 311                                         }
 312
 313                                         new_storey = new_storey.Resolve (ec);
 314                                         if (new_storey != null)
 315                                                 new_storey = Convert.ImplicitConversionRequired (ec, new_storey, host_method.MemberType, loc);
 316
 317                                         return true;
 318                                 }
 319
 320                                 protected override void DoEmit (EmitContext ec)
 321                                 {
 322                                         Label label_init = ec.DefineLabel ();
 323
 324                                         ec.EmitThis ();
 325                                         ec.Emit (OpCodes.Ldflda, host.PC.Spec);
 326                                         ec.EmitInt ((int) State.Start);
 327                                         ec.EmitInt ((int) State.Uninitialized);
 328
 329                                         var m = ec.Module.PredefinedMembers.InterlockedCompareExchange.Resolve (loc);
 330                                         if (m != null)
 331                                                 ec.Emit (OpCodes.Call, m);
 332
 333                                         ec.EmitInt ((int) State.Uninitialized);
 334                                         ec.Emit (OpCodes.Bne_Un_S, label_init);
 335
 336                                         ec.EmitThis ();
 337                                         ec.Emit (OpCodes.Ret);
 338
 339                                         ec.MarkLabel (label_init);
 340
 341                                         new_storey.Emit (ec);
 342                                         ec.Emit (OpCodes.Ret);
 343                                 }
 344
 345                                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 346                                 {
 347                                         throw new NotImplementedException ();
 348                                 }
 349
 350                                 public override Reachability MarkReachable (Reachability rc)
 351                                 {
 352                                         base.MarkReachable (rc);
 353                                         return Reachability.CreateUnreachable ();
 354                                 }
 355                         }
 356
 357                         GetEnumeratorMethod (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 358                                 : base (host, null, returnType, Modifiers.DEBUGGER_HIDDEN, name, ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis)
 359                         {
 360                         }
 361
 362                         public static GetEnumeratorMethod Create (IteratorStorey host, FullNamedExpression returnType, MemberName name)
 363                         {
 364                                 return Create (host, returnType, name, null);
 365                         }
 366
 367                         public static GetEnumeratorMethod Create (IteratorStorey host, FullNamedExpression returnType, MemberName name, Statement statement)
 368                         {
 369                                 var m = new GetEnumeratorMethod (host, returnType, name);
 370                                 var stmt = statement ?? new GetEnumeratorStatement (host, m);
 371                                 m.block.AddStatement (stmt);
 372                                 return m;
 373                         }
 374                 }
 375
 376                 class DisposeMethod : StateMachineMethod
 377                 {
 378                         sealed class DisposeMethodStatement : Statement
 379                         {
 380                                 Iterator iterator;
 381
 382                                 public DisposeMethodStatement (Iterator iterator)
 383                                 {
 384                                         this.iterator = iterator;
 385                                         this.loc = iterator.Location;
 386                                 }
 387
 388                                 protected override void CloneTo (CloneContext clonectx, Statement target)
 389                                 {
 390                                         throw new NotSupportedException ();
 391                                 }
 392
 393                                 public override bool Resolve (BlockContext ec)
 394                                 {
 395                                         return true;
 396                                 }
 397
 398                                 protected override void DoEmit (EmitContext ec)
 399                                 {
 400                                         ec.CurrentAnonymousMethod = iterator;
 401                                         iterator.EmitDispose (ec);
 402                                 }
 403
 404                                 protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 405                                 {
 406                                         throw new NotImplementedException ();
 407                                 }
 408                         }
 409
 410                         public DisposeMethod (IteratorStorey host)
 411                                 : base (host, null, new TypeExpression (host.Compiler.BuiltinTypes.Void, host.Location), Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN,
 412                                         new MemberName ("Dispose", host.Location), ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis)
 413                         {
 414                                 host.Members.Add (this);
 415
 416                                 Block.AddStatement (new DisposeMethodStatement (host.Iterator));
 417                         }
 418                 }
 419
 420                 //
 421                 // Uses Method as method info
 422                 //
 423                 class DynamicMethodGroupExpr : MethodGroupExpr
 424                 {
 425                         readonly Method method;
 426
 427                         public DynamicMethodGroupExpr (Method method, Location loc)
 428                                 : base ((IList<MemberSpec>) null, null, loc)
 429                         {
 430                                 this.method = method;
 431                                 eclass = ExprClass.Unresolved;
 432                         }
 433
 434                         protected override Expression DoResolve (ResolveContext ec)
 435                         {
 436                                 Methods = new List<MemberSpec> (1) { method.Spec };
 437                                 type = method.Parent.Definition;
 438                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 439                                 return base.DoResolve (ec);
 440                         }
 441                 }
 442
 443                 class DynamicFieldExpr : FieldExpr
 444                 {
 445                         readonly Field field;
 446
 447                         public DynamicFieldExpr (Field field, Location loc)
 448                                 : base (loc)
 449                         {
 450                                 this.field = field;
 451                         }
 452
 453                         protected override Expression DoResolve (ResolveContext ec)
 454                         {
 455                                 spec = field.Spec;
 456                                 type = spec.MemberType;
 457                                 InstanceExpression = new CompilerGeneratedThis (type, Location);
 458                                 return base.DoResolve (ec);
 459                         }
 460                 }
 461
 462                 public readonly Iterator Iterator;
 463
 464                 List<HoistedParameter> hoisted_params_copy;
 465
 466                 TypeExpr iterator_type_expr;
 467                 Field current_field;
 468                 Field disposing_field;
 469
 470                 TypeSpec generic_enumerator_type;
 471                 TypeSpec generic_enumerable_type;
 472
 473                 public IteratorStorey (Iterator iterator)
 474                         : base (iterator.Container.ParametersBlock, iterator.Host,
 475                           iterator.OriginalMethod as MemberBase, iterator.OriginalMethod.CurrentTypeParameters, "Iterator", MemberKind.Class)
 476                 {
 477                         this.Iterator = iterator;
 478                 }
 479
 480                 public Field CurrentField {
 481                         get {
 482                                 return current_field;
 483                         }
 484                 }
 485
 486                 public Field DisposingField {
 487                         get {
 488                                 return disposing_field;
 489                         }
 490                 }
 491
 492                 public IList<HoistedParameter> HoistedParameters {
 493                         get { return hoisted_params; }
 494                 }
 495
 496                 protected override Constructor DefineDefaultConstructor (bool is_static)
 497                 {
 498                         var ctor = base.DefineDefaultConstructor (is_static);
 499                         ctor.ModFlags |= Modifiers.DEBUGGER_HIDDEN;
 500                         return ctor;
 501                 }
 502
 503                 protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
 504                 {
 505                         var mtype = Iterator.OriginalIteratorType;
 506                         if (Mutator != null)
 507                                 mtype = Mutator.Mutate (mtype);
 508
 509                         iterator_type_expr = new TypeExpression (mtype, Location);
 510
 511                         var ifaces = new List<TypeSpec> (5);
 512                         if (Iterator.IsEnumerable) {
 513                                 ifaces.Add (Compiler.BuiltinTypes.IEnumerable);
 514
 515                                 if (Module.PredefinedTypes.IEnumerableGeneric.Define ()) {
 516                                         generic_enumerable_type = Module.PredefinedTypes.IEnumerableGeneric.TypeSpec.MakeGenericType (Module, new[] { mtype });
 517                                         ifaces.Add (generic_enumerable_type);
 518                                 }
 519                         }
 520
 521                         ifaces.Add (Compiler.BuiltinTypes.IEnumerator);
 522                         ifaces.Add (Compiler.BuiltinTypes.IDisposable);
 523
 524                         var ienumerator_generic = Module.PredefinedTypes.IEnumeratorGeneric;
 525                         if (ienumerator_generic.Define ()) {
 526                                 generic_enumerator_type = ienumerator_generic.TypeSpec.MakeGenericType (Module, new [] { mtype });
 527                                 ifaces.Add (generic_enumerator_type);
 528                         }
 529
 530                         base_class = null;
 531
 532                         base_type = Compiler.BuiltinTypes.Object;
 533                         return ifaces.ToArray ();
 534                 }
 535
 536                 protected override bool DoDefineMembers ()
 537                 {
 538                         current_field = AddCompilerGeneratedField ("$current", iterator_type_expr);
 539                         disposing_field = AddCompilerGeneratedField ("$disposing", new TypeExpression (Compiler.BuiltinTypes.Bool, Location));
 540
 541                         if (Iterator.IsEnumerable && hoisted_params != null) {
 542                                 //
 543                                 // Iterators are independent, each GetEnumerator call has to
 544                                 // create same enumerator therefore we have to keep original values
 545                                 // around for re-initialization
 546                                 //
 547                                 hoisted_params_copy = new List<HoistedParameter> (hoisted_params.Count);
 548                                 foreach (HoistedParameter hp in hoisted_params) {
 549
 550                                         //
 551                                         // Don't create field copy for unmodified captured parameters
 552                                         //
 553                                         HoistedParameter hp_copy;
 554                                         if (hp.IsAssigned) {
 555                                                 hp_copy = new HoistedParameter (hp, "<$>" + hp.Field.Name);
 556                                         } else {
 557                                                 hp_copy = null;
 558                                         }
 559
 560                                         hoisted_params_copy.Add (hp_copy);
 561                                 }
 562                         }
 563
 564                         if (generic_enumerator_type != null)
 565                                 Define_Current (true);
 566
 567                         Define_Current (false);
 568                         new DisposeMethod (this);
 569                         Define_Reset ();
 570
 571                         if (Iterator.IsEnumerable) {
 572                                 FullNamedExpression explicit_iface = new TypeExpression (Compiler.BuiltinTypes.IEnumerable, Location);
 573                                 var name = new MemberName ("GetEnumerator", null, explicit_iface, Location.Null);
 574
 575                                 if (generic_enumerator_type != null) {
 576                                         explicit_iface = new TypeExpression (generic_enumerable_type, Location);
 577                                         var gname = new MemberName ("GetEnumerator", null, explicit_iface, Location.Null);
 578                                         Method gget_enumerator = GetEnumeratorMethod.Create (this, new TypeExpression (generic_enumerator_type, Location), gname);
 579
 580                                         //
 581                                         // Just call generic GetEnumerator implementation
 582                                         //
 583                                         var stmt = new Return (new Invocation (new DynamicMethodGroupExpr (gget_enumerator, Location), null), Location);
 584                                         Method get_enumerator = GetEnumeratorMethod.Create (this, new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location), name, stmt);
 585
 586                                         Members.Add (get_enumerator);
 587                                         Members.Add (gget_enumerator);
 588                                 } else {
 589                                         Members.Add (GetEnumeratorMethod.Create (this, new TypeExpression (Compiler.BuiltinTypes.IEnumerator, Location), name));
 590                                 }
 591                         }
 592
 593                         return base.DoDefineMembers ();
 594                 }
 595
 596                 void Define_Current (bool is_generic)
 597                 {
 598                         TypeExpr type;
 599                         FullNamedExpression explicit_iface;
 600
 601                         if (is_generic) {
 602                                 explicit_iface = new TypeExpression (generic_enumerator_type, Location);
 603                                 type = iterator_type_expr;
 604                         } else {
 605                                 explicit_iface = new TypeExpression (Module.Compiler.BuiltinTypes.IEnumerator, Location);
 606                                 type = new TypeExpression (Compiler.BuiltinTypes.Object, Location);
 607                         }
 608
 609                         var name = new MemberName ("Current", null, explicit_iface, Location);
 610
 611                         ToplevelBlock get_block = new ToplevelBlock (Compiler, ParametersCompiled.EmptyReadOnlyParameters, Location,
 612                                 Block.Flags.CompilerGenerated | Block.Flags.NoFlowAnalysis);
 613                         get_block.AddStatement (new Return (new DynamicFieldExpr (CurrentField, Location), Location));
 614
 615                         Property current = new Property (this, type, Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED, name, null);
 616                         current.Get = new Property.GetMethod (current, Modifiers.COMPILER_GENERATED, null, Location);
 617                         current.Get.Block = get_block;
 618
 619                         Members.Add (current);
 620                 }
 621
 622                 void Define_Reset ()
 623                 {
 624                         Method reset = new Method (
 625                                 this, new TypeExpression (Compiler.BuiltinTypes.Void, Location),
 626                                 Modifiers.PUBLIC | Modifiers.DEBUGGER_HIDDEN | Modifiers.COMPILER_GENERATED,
 627                                 new MemberName ("Reset", Location),
 628                                 ParametersCompiled.EmptyReadOnlyParameters, null);
 629                         Members.Add (reset);
 630
 631                         reset.Block = new ToplevelBlock (Compiler, reset.ParameterInfo, Location,
 632                                 Block.Flags.CompilerGenerated | Block.Flags.NoFlowAnalysis);
 633
 634                         TypeSpec ex_type = Module.PredefinedTypes.NotSupportedException.Resolve ();
 635                         if (ex_type == null)
 636                                 return;
 637
 638                         reset.Block.AddStatement (new Throw (new New (new TypeExpression (ex_type, Location), null, Location), Location));
 639                 }
 640
 641                 protected override void EmitHoistedParameters (EmitContext ec, List<HoistedParameter> hoisted)
 642                 {
 643                         base.EmitHoistedParameters (ec, hoisted);
 644                         if (hoisted_params_copy != null)
 645                                 base.EmitHoistedParameters (ec, hoisted_params_copy);
 646                 }
 647         }
 648
 649         public class StateMachineMethod : Method
 650         {
 651                 readonly StateMachineInitializer expr;
 652
 653                 public StateMachineMethod (StateMachine host, StateMachineInitializer expr, FullNamedExpression returnType,
 654                         Modifiers mod, MemberName name, ToplevelBlock.Flags blockFlags)
 655                         : base (host, returnType, mod | Modifiers.COMPILER_GENERATED,
 656                           name, ParametersCompiled.EmptyReadOnlyParameters, null)
 657                 {
 658                         this.expr = expr;
 659                         Block = new ToplevelBlock (host.Compiler, ParametersCompiled.EmptyReadOnlyParameters, Location.Null, blockFlags);
 660                 }
 661
 662                 public override EmitContext CreateEmitContext (ILGenerator ig, SourceMethodBuilder sourceMethod)
 663                 {
 664                         EmitContext ec = new EmitContext (this, ig, MemberType, sourceMethod);
 665                         ec.CurrentAnonymousMethod = expr;
 666
 667                         if (expr is AsyncInitializer)
 668                                 ec.With (BuilderContext.Options.AsyncBody, true);
 669
 670                         return ec;
 671                 }
 672         }
 673
 674         public abstract class StateMachineInitializer : AnonymousExpression
 675         {
 676                 sealed class MoveNextBodyStatement : Statement
 677                 {
 678                         readonly StateMachineInitializer state_machine;
 679
 680                         public MoveNextBodyStatement (StateMachineInitializer stateMachine)
 681                         {
 682                                 this.state_machine = stateMachine;
 683                                 this.loc = stateMachine.Location;
 684                         }
 685
 686                         protected override void CloneTo (CloneContext clonectx, Statement target)
 687                         {
 688                                 throw new NotSupportedException ();
 689                         }
 690
 691                         public override bool Resolve (BlockContext ec)
 692                         {
 693                                 return true;
 694                         }
 695
 696                         protected override void DoEmit (EmitContext ec)
 697                         {
 698                                 state_machine.EmitMoveNext (ec);
 699                         }
 700
 701                         public override void Emit (EmitContext ec)
 702                         {
 703                                 // Don't create sequence point
 704                                 DoEmit (ec);
 705                         }
 706
 707                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
 708                         {
 709                                 return state_machine.ReturnType.Kind != MemberKind.Void;
 710                         }
 711
 712                         public override Reachability MarkReachable (Reachability rc)
 713                         {
 714                                 base.MarkReachable (rc);
 715
 716                                 if (state_machine.ReturnType.Kind != MemberKind.Void)
 717                                         rc = Reachability.CreateUnreachable ();
 718
 719                                 return rc;
 720                         }
 721                 }
 722
 723                 public readonly TypeDefinition Host;
 724                 protected StateMachine storey;
 725
 726                 //
 727                 // The state as we generate the machine
 728                 //
 729                 protected Label move_next_ok;
 730                 protected Label move_next_error;
 731                 LocalBuilder skip_finally;
 732                 protected LocalBuilder current_pc;
 733                 protected List<ResumableStatement> resume_points;
 734
 735                 protected StateMachineInitializer (ParametersBlock block, TypeDefinition host, TypeSpec returnType)
 736                         : base (block, returnType, block.StartLocation)
 737                 {
 738                         this.Host = host;
 739                 }
 740
 741                 #region Properties
 742
 743                 public Label BodyEnd { get; set; }
 744
 745                 public LocalBuilder CurrentPC
 746                 {
 747                         get {
 748                                 return current_pc;
 749                         }
 750                 }
 751
 752                 public LocalBuilder SkipFinally {
 753                         get {
 754                                 return skip_finally;
 755                         }
 756                 }
 757
 758                 public override AnonymousMethodStorey Storey {
 759                         get {
 760                                 return storey;
 761                         }
 762                 }
 763
 764                 #endregion
 765
 766                 public int AddResumePoint (ResumableStatement stmt)
 767                 {
 768                         if (resume_points == null)
 769                                 resume_points = new List<ResumableStatement> ();
 770
 771                         resume_points.Add (stmt);
 772                         return resume_points.Count;
 773                 }
 774
 775                 public override Expression CreateExpressionTree (ResolveContext ec)
 776                 {
 777                         throw new NotSupportedException ("ET");
 778                 }
 779
 780                 protected virtual BlockContext CreateBlockContext (BlockContext bc)
 781                 {
 782                         var ctx = new BlockContext (bc, block, bc.ReturnType);
 783                         ctx.CurrentAnonymousMethod = this;
 784
 785                         ctx.AssignmentInfoOffset = bc.AssignmentInfoOffset;
 786                         ctx.EnclosingLoop = bc.EnclosingLoop;
 787                         ctx.EnclosingLoopOrSwitch = bc.EnclosingLoopOrSwitch;
 788                         ctx.Switch = bc.Switch;
 789
 790                         return ctx;
 791                 }
 792
 793                 protected override Expression DoResolve (ResolveContext rc)
 794                 {
 795                         var bc = (BlockContext) rc;
 796                         var ctx = CreateBlockContext (bc);
 797
 798                         Block.Resolve (ctx);
 799
 800                         if (!rc.IsInProbingMode) {
 801                                 var move_next = new StateMachineMethod (storey, this, new TypeExpression (ReturnType, loc), Modifiers.PUBLIC, new MemberName ("MoveNext", loc), 0);
 802                                 move_next.Block.AddStatement (new MoveNextBodyStatement (this));
 803                                 storey.AddEntryMethod (move_next);
 804                         }
 805
 806                         bc.AssignmentInfoOffset = ctx.AssignmentInfoOffset;
 807                         eclass = ExprClass.Value;
 808                         return this;
 809                 }
 810
 811                 public override void Emit (EmitContext ec)
 812                 {
 813                         //
 814                         // Load state machine instance
 815                         //
 816                         storey.Instance.Emit (ec);
 817                 }
 818
 819                 void EmitMoveNext_NoResumePoints (EmitContext ec)
 820                 {
 821                         ec.EmitThis ();
 822                         ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
 823
 824                         ec.EmitThis ();
 825                         ec.EmitInt ((int) IteratorStorey.State.After);
 826                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 827
 828                         // We only care if the PC is zero (start executing) or non-zero (don't do anything)
 829                         ec.Emit (OpCodes.Brtrue, move_next_error);
 830
 831                         BodyEnd = ec.DefineLabel ();
 832
 833                         var async_init = this as AsyncInitializer;
 834                         if (async_init != null)
 835                                 ec.BeginExceptionBlock ();
 836
 837                         block.EmitEmbedded (ec);
 838
 839                         if (async_init != null)
 840                                 async_init.EmitCatchBlock (ec);
 841
 842                         ec.MarkLabel (BodyEnd);
 843
 844                         EmitMoveNextEpilogue (ec);
 845
 846                         ec.MarkLabel (move_next_error);
 847
 848                         if (ReturnType.Kind != MemberKind.Void) {
 849                                 ec.EmitInt (0);
 850                                 ec.Emit (OpCodes.Ret);
 851                         }
 852
 853                         ec.MarkLabel (move_next_ok);
 854                 }
 855
 856                 void EmitMoveNext (EmitContext ec)
 857                 {
 858                         move_next_ok = ec.DefineLabel ();
 859                         move_next_error = ec.DefineLabel ();
 860
 861                         if (resume_points == null) {
 862                                 EmitMoveNext_NoResumePoints (ec);
 863                                 return;
 864                         }
 865
 866                         current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
 867                         ec.EmitThis ();
 868                         ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
 869                         ec.Emit (OpCodes.Stloc, current_pc);
 870
 871                         // We're actually in state 'running', but this is as good a PC value as any if there's an abnormal exit
 872                         ec.EmitThis ();
 873                         ec.EmitInt ((int) IteratorStorey.State.After);
 874                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 875
 876                         Label[] labels = new Label[1 + resume_points.Count];
 877                         labels[0] = ec.DefineLabel ();
 878
 879                         bool need_skip_finally = false;
 880                         for (int i = 0; i < resume_points.Count; ++i) {
 881                                 ResumableStatement s = resume_points[i];
 882                                 need_skip_finally |= s is ExceptionStatement;
 883                                 labels[i + 1] = s.PrepareForEmit (ec);
 884                         }
 885
 886                         if (need_skip_finally) {
 887                                 skip_finally = ec.GetTemporaryLocal (ec.BuiltinTypes.Bool);
 888                                 ec.EmitInt (0);
 889                                 ec.Emit (OpCodes.Stloc, skip_finally);
 890                         }
 891
 892                         var async_init = this as AsyncInitializer;
 893                         if (async_init != null)
 894                                 ec.BeginExceptionBlock ();
 895
 896                         ec.Emit (OpCodes.Ldloc, current_pc);
 897                         ec.Emit (OpCodes.Switch, labels);
 898
 899                         ec.Emit (async_init != null ? OpCodes.Leave : OpCodes.Br, move_next_error);
 900
 901                         ec.MarkLabel (labels[0]);
 902
 903                         BodyEnd = ec.DefineLabel ();
 904
 905                         block.EmitEmbedded (ec);
 906
 907                         ec.MarkLabel (BodyEnd);
 908
 909                         if (async_init != null) {
 910                                 async_init.EmitCatchBlock (ec);
 911                         }
 912
 913                         ec.Mark (Block.Original.EndLocation);
 914                         ec.EmitThis ();
 915                         ec.EmitInt ((int) IteratorStorey.State.After);
 916                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 917
 918                         EmitMoveNextEpilogue (ec);
 919
 920                         ec.MarkLabel (move_next_error);
 921
 922                         if (ReturnType.Kind != MemberKind.Void) {
 923                                 ec.EmitInt (0);
 924                                 ec.Emit (OpCodes.Ret);
 925                         }
 926
 927                         ec.MarkLabel (move_next_ok);
 928
 929                         if (ReturnType.Kind != MemberKind.Void) {
 930                                 ec.EmitInt (1);
 931                                 ec.Emit (OpCodes.Ret);
 932                         }
 933                 }
 934
 935                 protected virtual void EmitMoveNextEpilogue (EmitContext ec)
 936                 {
 937                 }
 938
 939                 public void EmitLeave (EmitContext ec, bool unwind_protect)
 940                 {
 941                         // Return ok
 942                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_ok);
 943                 }
 944
 945                 //
 946                 // Called back from YieldStatement
 947                 //
 948                 public virtual void InjectYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
 949                 {
 950                         //
 951                         // Guard against being disposed meantime
 952                         //
 953                         Label disposed = ec.DefineLabel ();
 954                         var iterator = storey as IteratorStorey;
 955                         if (iterator != null) {
 956                                 ec.EmitThis ();
 957                                 ec.Emit (OpCodes.Ldfld, iterator.DisposingField.Spec);
 958                                 ec.Emit (OpCodes.Brtrue_S, disposed);
 959                         }
 960
 961                         //
 962                         // store resume program-counter
 963                         //
 964                         ec.EmitThis ();
 965                         ec.EmitInt (resume_pc);
 966                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
 967
 968                         if (iterator != null) {
 969                                 ec.MarkLabel (disposed);
 970                         }
 971
 972                         // mark finally blocks as disabled
 973                         if (unwind_protect && skip_finally != null) {
 974                                 ec.EmitInt (1);
 975                                 ec.Emit (OpCodes.Stloc, skip_finally);
 976                         }
 977                 }
 978
 979                 public void SetStateMachine (StateMachine stateMachine)
 980                 {
 981                         this.storey = stateMachine;
 982                 }
 983         }
 984
 985         //
 986         // Iterators are implemented as state machine blocks
 987         //
 988         public class Iterator : StateMachineInitializer
 989         {
 990                 sealed class TryFinallyBlockProxyStatement : Statement
 991                 {
 992                         TryFinallyBlock block;
 993                         Iterator iterator;
 994
 995                         public TryFinallyBlockProxyStatement (Iterator iterator, TryFinallyBlock block)
 996                         {
 997                                 this.iterator = iterator;
 998                                 this.block = block;
 999                         }
1000
1001                         protected override void CloneTo (CloneContext clonectx, Statement target)
1002                         {
1003                                 throw new NotSupportedException ();
1004                         }
1005
1006                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
1007                         {
1008                                 throw new NotSupportedException ();
1009                         }
1010
1011                         protected override void DoEmit (EmitContext ec)
1012                         {
1013                                 //
1014                                 // Restore redirection for any captured variables
1015                                 //
1016                                 ec.CurrentAnonymousMethod = iterator;
1017
1018                                 using (ec.With (BuilderContext.Options.OmitDebugInfo, !ec.HasMethodSymbolBuilder)) {
1019                                         block.EmitFinallyBody (ec);
1020                                 }
1021                         }
1022                 }
1023
1024                 public readonly IMethodData OriginalMethod;
1025                 public readonly bool IsEnumerable;
1026                 public readonly TypeSpec OriginalIteratorType;
1027                 int finally_hosts_counter;
1028
1029                 public Iterator (ParametersBlock block, IMethodData method, TypeDefinition host, TypeSpec iterator_type, bool is_enumerable)
1030                         : base (block, host, host.Compiler.BuiltinTypes.Bool)
1031                 {
1032                         this.OriginalMethod = method;
1033                         this.OriginalIteratorType = iterator_type;
1034                         this.IsEnumerable = is_enumerable;
1035                         this.type = method.ReturnType;
1036                 }
1037
1038                 #region Properties
1039
1040                 public ToplevelBlock Container {
1041                         get { return OriginalMethod.Block; }
1042                 }
1043
1044                 public override string ContainerType {
1045                         get { return "iterator"; }
1046                 }
1047
1048                 public override bool IsIterator {
1049                         get { return true; }
1050                 }
1051
1052                 #endregion
1053
1054                 public Method CreateFinallyHost (TryFinallyBlock block)
1055                 {
1056                         var method = new Method (storey, new TypeExpression (storey.Compiler.BuiltinTypes.Void, loc),
1057                                 Modifiers.COMPILER_GENERATED, new MemberName (CompilerGeneratedContainer.MakeName (null, null, "Finally", finally_hosts_counter++), loc),
1058                                 ParametersCompiled.EmptyReadOnlyParameters, null);
1059
1060                         method.Block = new ToplevelBlock (method.Compiler, method.ParameterInfo, loc,
1061                                 ToplevelBlock.Flags.CompilerGenerated | ToplevelBlock.Flags.NoFlowAnalysis);
1062                         method.Block.AddStatement (new TryFinallyBlockProxyStatement (this, block));
1063
1064                         // Cannot it add to storey because it'd be emitted before nested
1065                         // anonoymous methods which could capture shared variable
1066
1067                         return method;
1068                 }
1069
1070                 public void EmitYieldBreak (EmitContext ec, bool unwind_protect)
1071                 {
1072                         ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, move_next_error);
1073                 }
1074
1075                 public override string GetSignatureForError ()
1076                 {
1077                         return OriginalMethod.GetSignatureForError ();
1078                 }
1079
1080                 public override void Emit (EmitContext ec)
1081                 {
1082                         //
1083                         // Load Iterator storey instance
1084                         //
1085                         storey.Instance.Emit (ec);
1086
1087                         //
1088                         // Initialize iterator PC when it's unitialized
1089                         //
1090                         if (IsEnumerable) {
1091                                 ec.Emit (OpCodes.Dup);
1092                                 ec.EmitInt ((int)IteratorStorey.State.Uninitialized);
1093
1094                                 var field = storey.PC.Spec;
1095                                 if (storey.MemberName.IsGeneric) {
1096                                         field = MemberCache.GetMember (Storey.Instance.Type, field);
1097                                 }
1098
1099                                 ec.Emit (OpCodes.Stfld, field);
1100                         }
1101                 }
1102
1103                 public void EmitDispose (EmitContext ec)
1104                 {
1105                         if (resume_points == null)
1106                                 return;
1107
1108                         Label end = ec.DefineLabel ();
1109
1110                         Label[] labels = null;
1111                         for (int i = 0; i < resume_points.Count; ++i) {
1112                                 ResumableStatement s = resume_points[i];
1113                                 Label ret = s.PrepareForDispose (ec, end);
1114                                 if (ret.Equals (end) && labels == null)
1115                                         continue;
1116                                 if (labels == null) {
1117                                         labels = new Label[resume_points.Count + 1];
1118                                         for (int j = 0; j <= i; ++j)
1119                                                 labels[j] = end;
1120                                 }
1121
1122                                 labels[i + 1] = ret;
1123                         }
1124
1125                         if (labels != null) {
1126                                 current_pc = ec.GetTemporaryLocal (ec.BuiltinTypes.UInt);
1127                                 ec.EmitThis ();
1128                                 ec.Emit (OpCodes.Ldfld, storey.PC.Spec);
1129                                 ec.Emit (OpCodes.Stloc, current_pc);
1130                         }
1131
1132                         ec.EmitThis ();
1133                         ec.EmitInt (1);
1134                         ec.Emit (OpCodes.Stfld, ((IteratorStorey) storey).DisposingField.Spec);
1135
1136                         ec.EmitThis ();
1137                         ec.EmitInt ((int) IteratorStorey.State.After);
1138                         ec.Emit (OpCodes.Stfld, storey.PC.Spec);
1139
1140                         if (labels != null) {
1141                                 //SymbolWriter.StartIteratorDispatcher (ec.ig);
1142                                 ec.Emit (OpCodes.Ldloc, current_pc);
1143                                 ec.Emit (OpCodes.Switch, labels);
1144                                 //SymbolWriter.EndIteratorDispatcher (ec.ig);
1145
1146                                 foreach (ResumableStatement s in resume_points)
1147                                         s.EmitForDispose (ec, current_pc, end, true);
1148                         }
1149
1150                         ec.MarkLabel (end);
1151                 }
1152
1153                 public override void EmitStatement (EmitContext ec)
1154                 {
1155                         throw new NotImplementedException ();
1156                 }
1157
1158                 public override void InjectYield (EmitContext ec, Expression expr, int resume_pc, bool unwind_protect, Label resume_point)
1159                 {
1160                         // Store the new value into current
1161                         var fe = new FieldExpr (((IteratorStorey) storey).CurrentField, loc);
1162                         fe.InstanceExpression = new CompilerGeneratedThis (storey.CurrentType, loc);
1163                         fe.EmitAssign (ec, expr, false, false);
1164
1165                         base.InjectYield (ec, expr, resume_pc, unwind_protect, resume_point);
1166
1167                         EmitLeave (ec, unwind_protect);
1168
1169                         ec.MarkLabel (resume_point);
1170                 }
1171
1172                 public static void CreateIterator (IMethodData method, TypeDefinition parent, Modifiers modifiers)
1173                 {
1174                         bool is_enumerable;
1175                         TypeSpec iterator_type;
1176
1177                         TypeSpec ret = method.ReturnType;
1178                         if (ret == null)
1179                                 return;
1180
1181                         if (!CheckType (ret, parent, out iterator_type, out is_enumerable)) {
1182                                 parent.Compiler.Report.Error (1624, method.Location,
1183                                               "The body of `{0}' cannot be an iterator block " +
1184                                               "because `{1}' is not an iterator interface type",
1185                                               method.GetSignatureForError (),
1186                                               ret.GetSignatureForError ());
1187                                 return;
1188                         }
1189
1190                         ParametersCompiled parameters = method.ParameterInfo;
1191                         for (int i = 0; i < parameters.Count; i++) {
1192                                 Parameter p = parameters [i];
1193                                 Parameter.Modifier mod = p.ModFlags;
1194                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
1195                                         parent.Compiler.Report.Error (1623, p.Location,
1196                                                 "Iterators cannot have ref or out parameters");
1197                                         return;
1198                                 }
1199
1200                                 if (p is ArglistParameter) {
1201                                         parent.Compiler.Report.Error (1636, method.Location,
1202                                                 "__arglist is not allowed in parameter list of iterators");
1203                                         return;
1204                                 }
1205
1206                                 if (parameters.Types [i].IsPointer) {
1207                                         parent.Compiler.Report.Error (1637, p.Location,
1208                                                 "Iterators cannot have unsafe parameters or yield types");
1209                                         return;
1210                                 }
1211                         }
1212
1213                         if ((modifiers & Modifiers.UNSAFE) != 0) {
1214                                 parent.Compiler.Report.Error (1629, method.Location, "Unsafe code may not appear in iterators");
1215                         }
1216
1217                         method.Block = method.Block.ConvertToIterator (method, parent, iterator_type, is_enumerable);
1218                 }
1219
1220                 static bool CheckType (TypeSpec ret, TypeContainer parent, out TypeSpec original_iterator_type, out bool is_enumerable)
1221                 {
1222                         original_iterator_type = null;
1223                         is_enumerable = false;
1224
1225                         if (ret.BuiltinType == BuiltinTypeSpec.Type.IEnumerable) {
1226                                 original_iterator_type = parent.Compiler.BuiltinTypes.Object;
1227                                 is_enumerable = true;
1228                                 return true;
1229                         }
1230                         if (ret.BuiltinType == BuiltinTypeSpec.Type.IEnumerator) {
1231                                 original_iterator_type = parent.Compiler.BuiltinTypes.Object;
1232                                 is_enumerable = false;
1233                                 return true;
1234                         }
1235
1236                         InflatedTypeSpec inflated = ret as InflatedTypeSpec;
1237                         if (inflated == null)
1238                                 return false;
1239
1240                         var member_definition = inflated.MemberDefinition;
1241                         PredefinedType ptype = parent.Module.PredefinedTypes.IEnumerableGeneric;
1242
1243                         if (ptype.Define () && ptype.TypeSpec.MemberDefinition == member_definition) {
1244                                 original_iterator_type = inflated.TypeArguments[0];
1245                                 is_enumerable = true;
1246                                 return true;
1247                         }
1248
1249                         ptype = parent.Module.PredefinedTypes.IEnumeratorGeneric;
1250                         if (ptype.Define () && ptype.TypeSpec.MemberDefinition == member_definition) {
1251                                 original_iterator_type = inflated.TypeArguments[0];
1252                                 is_enumerable = false;
1253                                 return true;
1254                         }
1255
1256                         return false;
1257                 }
1258         }
1259 }
1260